The IEEE 802.15.4-2015 defines a transmission and reception method of Time-Slotted Channel Hopping (TSCH). In the TSCH, communication with high reliability can be performed by matching communication timings in advance between communication nodes. By using a 6top Protocol being formulated by IETF 6TiSCH WG, communication timings of TSCH can be dynamically matched between neighbor nodes.
Nevertheless, in the conventional technology, a communication efficiency declines in some cases. For example, in the TSCH, a time slot being a time division unit in a time-division multiplex method is set. The length of the time slot (slot length) affects a communication efficiency. In a case where a data length of data to be transmitted or received is small, if a slot length is small, a communication efficiency can be enhanced. On the other hand, if a slot length is large with respect to a data length of data to be transmitted or received, a communication efficiency can possibly decline.